Add PSS info to dumpsys output.

We now track the last 12 hours of PSS measurements in SysUI
and emit them in bugreports.

While we're at it, tidy up some of the heap dumping code
(dump on separate thread, update tile state, tweak sharing
extras to fix filename when sharing to Drive).

Bug: 133671238
Test: adb shell dumpsys activity service SystemUI
Change-Id: I862f6e78ed49cf669786610fec0768ebb3b24438